Molded catching elements and method for manufacturing same

Abstract

The invention relates to a catching element of a male-female or male-male self-gripping device, which comprises a rod portion ( 1 ) and a catching portion ( 2 ), the rod portion extending in an axis that is transverse to a base strip (B) and the catching portion projecting laterally from the rod portion, characterized in that at least the catching portion is made of a thermoplastic material having a bending modulus of more than 1000 MPa, specifically more than 1200 MPa, in particular more than 1500 MPa at 25° C., the catching element being produced by molding, specifically by injection molding, and when the thermogram is plotted for the hook, in other words when differential scanning calorimetry is carried out, an absence or almost-absence of relaxation enthalpy near the glass transition can be seen during the first rise in temperature.

The invention claimed is: 
     
       1. A catching element of a male-female or male-male touch-and-close device which comprises a shank part and a catching part, the shank part extending along an axis transverse to a base band and the catching part protruding laterally from the shank part, characterized in that at least the catching part is made of a thermoplastic having a flexural modulus greater than 1000 MPa at 25° C., the catching element being produced by molding, notably injection molding, and when the thermogram for the catching element is plotted, namely when differential scanning calorimetry is performed, an absence or near-absence of relaxation enthalpy in the vicinity of the glass transition is noticed at the first rise in temperature. 
     
     
       2. The element as claimed in  claim 1 , characterized in that the absence or near-absence of relaxation enthalpy corresponds on the DSC curve to a specific relaxation enthalpy less than or equal to 1 J/g, the specific relaxation enthalpy being the ratio of the area between the curve on the first temperature rise and the curve on the second temperature rise in a zone ranging from Tg to Tg−30° C., divided by the mass of the sample. 
     
     
       3. The element as claimed in  claim 1 , characterized in that the absence or near-absence of relaxation enthalpy corresponds to the absence of a peak or maximum point for the curve of the first rise in temperature of the DSC in a zone comprised between Tg and Tg−30° C. 
     
     
       4. The element as claimed in  claim 1 , characterized in that the shank part is also made of a thermoplastic having a flexural modulus greater than 1000 MPa at 25° C., and notably is made of the same material as the catching part. 
     
     
       5. The element as claimed in  claim 4 , characterized in that the thermoplastic of the shank part has a flexural modulus greater than 1200 MPa at 25° C. 
     
     
       6. The element as claimed in  claim 4 , characterized in that the thermoplastic of the shank part has a flexural modulus greater than 1500 MPa at 25° C. 
     
     
       7. The element as claimed in  claim 1 , characterized in that the thermoplastic is an amorphous or substantially amorphous material. 
     
     
       8. The element as claimed in  claim 1 , characterized in that the thermoplastic of the catching part has a flexural modulus greater than 1200 MPa. 
     
     
       9. The element as claimed in  claim 1 , characterized in that the thermoplastic of the catching part has a flexural modulus greater than 1500 MPa at 25° C. 
     
     
       10. The element as claimed in  claim 7 , characterized in that the amorphous thermoplastic is chosen from the list comprising ABS, PC, PMMA, PVC, PEI, PES and polystyrene. 
     
     
       11. The element as claimed in  claim 1 , characterized in that the element has the shape of a mushroom, and notably the head part protrudes laterally from the shank part over 360° around the shank part. 
     
     
       12. The element as claimed in  claim 1 , characterized in that the catching part protrudes laterally from the shank section in at least three angularly separated angular sectors. 
     
     
       13. A method of manufacturing a catching element comprising a shank part extending from a base band along a shank axis transverse to the base band and a catching part protruding laterally from the shank in a direction transverse to the axis of the shank, which method comprises the following steps:
 a molding cavity of a shape that complements the catching element is provided; 
 the molding thermoplastic is introduced into the molding cavity in a form that can flow, notably in a viscous or pasty form; 
 the temperature of the thermoplastic inside the molding cavity is regulated to a value Tmold comprised between Tg−ΔTg and Tg+ΔTg, Tg being the glass transition temperature of the thermoplastic and ΔTg being equal to about 30° C.; 
 the element is demolded at this temperature Tmold; and 
 the demolded element is left to cool at a temperature lower than Tmold, notably at ambient temperature. 
 
     
     
       14. The method of  claim 13 , wherein ΔTg being equal to about 15° C.